Phase I funding will support the development of a prototype Elisa antigen capture kit to measure HTLV-1 is linked to the development of adult T- cell leukemia and to tropical spastic paraparesis, a neurological disease with interest to researchers on multiple sclerosis. Tracking the progress of HTLV-I infection in tissue cultures is more difficult than tracking HIV infection: HTLV-I seldom kills the cells it infects and the reverse transcriptase (RT) it produces is not very active in current RT assays. Therefore a commercial kit which measures the core proteins produced during infection will be valuable in studies of HTLV-I in tissue culture. The prototype assay will use p19 and p24 antibodies available in-house as capture antibodies. Hyperimmune rabbit sera specific for purified p19 and p24 will be developed and used as the detector antibodies. The prototype assay will be more sensitive than RT assays in tracking HTLV-1 infection but its sensitivity will be limited by the current lack of very high affinity monoclonal antibodies for p19 and p24. Production of high affinity monoclonal antibodies will begin Phase I.